Abstract

Women with polycystic ovary syndrome (PCOS) exhibit elevated androgen levels, oligo-anovulation, infertility, and insulin resistance in metabolic tissues. The aims of these studies were to determine the role of insulin signaling in the development and function of ovarian theca cells, and the pathophysiologic effects of hyperinsulinism on ovarian function in obesity. We disrupted the insulin receptor (IR) gene specifically in the theca interstitial (TI) cells of the ovaries (Cyp17IRKO). No changes in reproductive development or function were observed in lean Cyp17IRKO female mice suggesting that insulin signaling in TI cell is not essential for reproduction. However, when females were fed a high fat diet (Diet Induced Obesity (DIO)), DIO-WT mice were infertile and experienced increased circulating testosterone levels, while DIO-Cyp17IRKO mice exhibited improved fertility and testosterone levels comparable to those found in lean mice. The levels of pIRS1 and CYP17 protein were higher in the ovary of DIO-WT compared to DIO-Cyp17IRKO or lean mice. Ex vivo studies using a whole ovary culture model demonstrated that insulin acts independently or additively with hCG to enhance androstenedione secretion. These studies reveal the causal pathway linking hyperinsulinism with ovarian hyperandrogenism and the infertility of obesity.